Conventionally, as a system that connects a plurality of channels there exists a communication system that uses an ISDN network 51 as shown in FIG. 8. According to this communication system, using a plurality of wired channels, a telephone set 54 and a personal computer (PC) 55, each of which is an independent communication terminal, are connected with the ISDN network 51 through digital channel terminating equipment (DSU: Digital Service Unit) 52 and a TA (Terminal Adapter) 3. Each terminal makes communications with a communication terminal (not shown) which is connected with the ISDN network 51 with which the connection has been set up.
In such a system, when communications are made over multiple channels, as many terminals as the channels are needed. That is, when an operator simultaneously makes communications over multiple channels, it is required, for example, for the operator to keep multiple terminals at hand and to watch user information and status indications provided visibly and audibly to user interfaces, such as displays of the respective terminals, so as not to overlook them. For this reason, when the operator is paying much attention to communications such as TV telephone communications, even if a message communication has come in another terminal, the operator overlooks the information or cannot pay much attention to the TV telephone communications. Thus, a problem arises in that the operability is degraded considerably.
In addition, there are also problems that, since each terminal has a key entry section, the operation becomes complicated and, when an informing sound is emitted, it is unknown which terminal it is emitted from.
These terminals each have a channel interface (I/F), a controller, and an man-machine interface, such as keys and a display, built in. That is, communications over multiple channels require as many signal processing circuits as the channels (terminals). In recent years, the processing capability of CPUs and the circuit integration have improved by leaps and bounds and signal and control processing for the multiple channels has become possible with a single controller (CPU). Nevertheless, since as many signal processing circuits as the communication channels have to be provided, there arises a problem in that cost and power dissipation increase.
Thus, the provision of multiple terminals and the provision of multiple man-machine interfaces particularly in radio communication terminals cause a problem of significant degradations in the quality of products, such as degraded operability, increased cost, and increased power dissipation.